JP5085847B2 - High-efficiency fuel cell power generation system with an expander for power generation - Google Patents

Abstract

A hydrogen fuel cell power system having improved efficiency comprises a fuel cell, a source of hydrogen gas, a compressor for creating a pressurized air stream, and a liquid supply which is heated by waste heat form the power system and evaporates into the pressurized air stream to produce a pressurized air and steam mixture. The pressurized air/steam mixture, which is preferably used as the oxidant in the fuel cell, is combusted with fuel in a burner to produce a high-temperature steam-laden exhaust stream. The high-temperature steam-laden exhaust stream drives an expander to produce a power output, and a power take-off from the expander uses the expander power to, for instance, drive an electrical generator, or drive other system components.; The evaporation of liquid can take place external to the fuel cell, or can take place directly within the fuel cell, preferably using a cooling liquid that is directly injected into the fuel cell. The fuel cell power system advantageously uses the low-temperature waste heat of the fuel cell to evaporate liquid into the pressurized air, resulting in a steam/air mixture having a relatively large expansion potential. The systems and related methods of the invention are applicable to a wide range of fuel cell power systems, including a "pure" or "non-hybrid" fuel cell power system, powered by hydrogen from either an external source, such as a hydrogen storage tank, or from "direct" reforming of a fuel at the anode. The invention is also applicable to integrated or "hybridized" fuel cell power systems which contain a local fuel reformer.; In these systems, the fuel cell is powered by hydrogen-containing reformate generated by the reformer.

Description

Related applications

  This application is filed with US patent application Ser. This is a continuation application of 10 / 335,538. The aforementioned US application is hereby incorporated by reference herein.

  A fuel cell is an electrochemical device that converts the chemical energy of a reaction into electrical energy. A fuel cell is composed of an anode, a cathode, and an electrolyte layer separating them. In operation, a reactant, typically hydrogen gas, is supplied to the anode, and an oxidant, typically air or other oxygen-containing gas, is supplied to the cathode. An electric current is generated by an electrochemical reaction occurring in the fuel cell. In general, a fuel cell power generation system is composed of an assembly of a plurality of cells often referred to as a stack, and can extract a higher voltage than a single cell.

  In recent years, fuel cells have become a useful energy source, and there is increasing interest in the use of fuel cells as small and portable power sources, including vehicular power applications. One of the reasons that hinders the widespread use of fuel cell power generation systems is the lack of extensive infrastructure for production and supply of fuel, particularly hydrogen, required for fuel cell operation. In order to overcome this problem, attempts have been made to use a hybrid power generation system (reforming fuel cell system) that operates on ordinary hydrocarbon fuel. In such a system, hydrocarbon fuel is first converted to reformed fuel containing hydrogen by an on-board fuel reformer incorporated in the system, and then the resulting reformed fuel is used to operate the fuel cell. Is done.

  In the future, non-hybrid or “pure” hydrogen fuel cell power generation systems (ie, reformers) where hydrogen is supplied by nearby hydrogen storage systems or (in stationary applications) directly from a remote source Is not expected to be more cost effective. Further, by supplying the fuel cell with an easily reformed fuel such as alcohol, particularly methanol, so that hydrogen can be generated on the anode of the fuel cell, it is not necessary to use a separate fuel reforming subsystem. .

  In any of these fuel cell-based power generation systems, especially in mobile or portable power generation applications, a slight improvement in system efficiency is critical in terms of system size, weight and cost effectiveness. Can make a big difference.

  The present invention generally relates to a power generation system based on a fuel cell with improved efficiency, and a fuel reformer / fuel cell is integrated in the power generation system based on the fuel cell. Includes reforming and “pure” hydrogen systems. In one aspect, the fuel cell system of the present invention advantageously utilizes the low temperature waste heat of the fuel cell to generate additional output, thereby improving overall system efficiency. The system has a fuel cell having an anode and a cathode, a source of hydrogen gas supplied to the anode of the fuel cell, and a compressor that generates a flow of pressurized air supplied to the cathode of the fuel cell. The cathode pressurized air stream and the anode hydrogen gas react in the fuel cell to produce electrical output and waste heat. The system further includes a cooling liquid (eg, water) that removes low temperature waste heat from the fuel cell. The cooling liquid is heated directly or indirectly by the waste heat of the power generation system and is preferably pressurized air, which is an oxidant air stream to, from, or in the fuel cell cathode. Vaporization in the stream produces a steam-containing pressurized air stream. This steam-containing air stream is then supplied to the burner along with fuel and burned to produce a hot steam-containing exhaust stream. This steam-containing exhaust stream drives an expander such as a turbine to provide output. The output from the expander usually exceeds the power required for the compression of the air, and the output of the expander is connected to the auxiliary structure of the system such as a compressor and a pump through the extraction of power. It can be used to drive the elements and / or can be used to supplement the system output from the fuel cell, such as by driving a generator.

  In some embodiments, the system has a cooling loop and fluid circulates through the system to remove waste heat from the fuel cell. The cooling liquid that vaporizes into the pressurized air may contain the fluid of this cooling loop or may be overheated by the fluid of this cooling loop.

  In other embodiments, the fuel cell is cooled by injecting a cooling liquid directly into the fuel cell. In this case, the cooling liquid can be vaporized in the pressurized air in the fuel cell.

  The present invention can achieve improved fuel cell and Brayton cycle efficiencies by advantageously utilizing low temperature waste heat from the fuel cell power generation system. Waste heat generated in ordinary low temperature fuel cells, such as the well-known “PEM” cell (polymer electrolyte membrane type or proton exchange membrane type cell; sometimes called solid polymer electrolyte membrane type cell) It is known to be difficult to recover in a way that produces useful output. For example, many low temperature fuel cells operate at temperatures below 200 ° C, and more typically operate at temperatures below 100 ° C. For example, current existing PEM fuel cells operate at temperatures between 50 ° C and 100 ° C. The temperature of these low temperature fuel cell thermal wastes is too low for energy recovery by conventional means such as a steam turbine or other Rankine type “bottoming cycle”. Thus, the waste heat of such a low temperature fuel cell is simply released to the environment by a closed loop radiator or other means.

  On the other hand, in the present invention, at least a part of this low-temperature waste heat uses the waste heat energy to vaporize water into the pressurized air, producing a pressurized steam / air stream with a large expansion potential. Is conveniently recovered. This steam / air mixture is then burned in a burner, which allows the system to generate a large additional power by expansion of the steam-containing burner exhaust. Steam provides an additional mass flow rate (ie, a mass flow with a regulated specific heat) through the expander compared to exhaust air alone. In essence, the present invention adds a Rankine cycle or steam cycle output addition to the Brayton turbo compressor bottoming cycle.

  In addition, the extra output of this expander comes from the recovery of low temperature “waste” heat by vaporizing warm water into pressurized air (ie, “partial pressure effect”), resulting in little or no cost. You can get without. The energy obtained is basically the latent heat consumed by water vaporization. The amount of latent heat is very large, requiring about 2326 joules per gram to vaporize 60 ° C. water, while about 1465 joules per gram to heat the vaporized water (steam) to 800 ° C. Only need to be added. The procedure of pressurizing air prior to water vaporization consumes significant energy to compress the air, while the energy required to compress water to the same pressure is extremely small, maximizing efficiency improvements. Is important to do.

  In some embodiments, the fuel cell power generation system comprises a fuel cell / fuel reformer integrated or “hybrid” system. In this system, a hydrogen source for a fuel cell is a fuel reformer that converts an input fuel, such as a common hydrocarbon fuel, into a hydrogen-containing reformed fuel via one or more chemical reactions ( Or a fuel processor). This reformed fuel is then used as fuel on the anode side of the fuel cell. In such a system, usually, heat is supplied using a burner to support a fuel reforming reaction that is an endothermic reaction. In some embodiments of the present invention, steam-containing exhaust from a fuel cell is supplied to a reformer burner and fuel (this fuel optionally comprises unused hydrogen discharged from the fuel cell). It can be burned together to produce steam-containing exhaust that drives the expander.

  In another embodiment, the fuel cell power generation system comprises a “pure” hydrogen fuel cell that is not hybridized. These fuel cells are not individually integrated with the reformer, but instead are operated with hydrogen from other sources such as stored hydrogen or hydrogen supplied from a remote location. Conventional “pure” hydrogen fuel cells do not have a burner because they do not need to support a fuel reforming reaction. In a typical device, hydrogen is supplied to the “dead end” anode side of the fuel cell. That is, hydrogen remains contained within the anode during operation. The contents of the cell, such as water and unreacted hydrogen, are periodically released to the environment by a “purge” cycle, and a new hydrogen supply is added to resume fuel cell operation.

  In contrast, the “pure” hydrogen fuel cell system of the present invention has a burner that burns fuel with a pressurized air / steam mixture to provide a steam-containing exhaust stream for driving the expander. ing. In some embodiments, the fuel burned in the burner contains unreacted hydrogen that is periodically or continuously recycled from the fuel cell anode. The fuel may also include additional fuel from the same source for supplying hydrogen to the fuel cell, such as a hydrogen storage tank. By vaporizing water warmed by waste heat into a pressurized oxidant stream before the oxidant enters the fuel cell, after leaving the fuel cell, and / or when in the fuel cell. At least a part of the waste heat from the power generation system is recovered. The resulting air / steam mixture is then optionally preheated by burner exhaust (which may optionally result in further water vaporization into the air) and then combusted with fuel to produce a steam containing burner exhaust. Is generated. This exhaust then expands in the expander, producing an output that effectively exceeds the power normally used to compress the air.

  The pure hydrogen fuel cell power generation system of the present invention advantageously uses a pressurized air stream as the cathode oxidant, resulting in improved fuel cell output or reduced fuel cell size for a given output. Furthermore, the performance generated by the increased air flow does not create an extra load because the output generated by the expansion of the steam-containing exhaust is more than enough to compensate for the power required to pressurize the air. Of course, the addition of a burner tends to reduce the efficiency of the system, usually because some additional fuel is consumed in the burner. However, the energy recovered from the waste heat of the system by vaporizing water into the pressurized cathode air stream is more than offset. The expansion of the steam-containing exhaust produces net energy that exceeds the cost of air compression and the extra fuel used in the burner, thus improving overall system efficiency. Moreover, the resulting system is usually very flexible and can respond instantaneously to transients.

  According to yet another aspect, the present invention includes a fuel cell power generation system and a method of operating such a system, the system comprising a fuel cell comprising an anode and a cathode, a fuel for generating power output A compressor for generating a pressurized air stream to be supplied to the cathode of the battery, in communication with the pressurized air stream, at least a part of which is heated by the waste heat of the power generation system, A cooling liquid that evaporates to produce a pressurized mixture of air and steam, a burner for combusting fuel with the pressurized steam / air mixture to produce an exhaust stream containing hot exhaust steam, and the exhaust It has an expander that is driven to produce output. In addition, the system includes a condenser, such as a radiator, to recover at least a portion of the liquid vaporized from the expanded burner exhaust before releasing the exhaust from the system. In some embodiments, the system further comprises a device for applying back pressure to the burner exhaust to facilitate recovery of the liquid vaporized from the burner exhaust. Back pressure can be selectively applied to increase the dew point of the exhaust stream, making it easier to recover the liquid in the exhaust, especially when the system is operating at high ambient temperatures. This technique involves a “pure” hydrogen fuel cell and a “hybrid” fuel cell with a “direct” fuel cell that directly converts fuel to hydrogen within the fuel cell, as well as an integrated fuel reformer subsystem. Applicable to power generation systems.

  The above objects, features and advantages of the present invention, as well as other objects, features and advantages will become apparent from the following more detailed description of the preferred embodiments of the present invention as illustrated in the accompanying drawings. In the accompanying drawings, the same reference numerals indicate the same parts in different drawings. The drawings are not necessarily to scale, emphasis may be placed upon illustrating the principles of the invention.

  The present invention relates generally to a method and apparatus for improving the operating efficiency of a fuel cell power generation system by recovering low temperature waste heat from the power generation system and converting this heat into useful energy. The power generation system described herein utilizes a fuel cell, which is a device that generates electrical power through an electrochemical reaction through the bulkhead of two reactants, typically hydrogen and oxygen. In general, a fuel cell takes out a voltage higher than a voltage obtained from a single fuel cell. Therefore, a plurality of cells are stacked to form a fuel cell “stack”. In this specification, when the expression “fuel cell” is used, it includes both a single fuel cell and a fuel cell “stack” unless otherwise specified.

  Fuel cells to which the present invention is particularly applicable include fuel cells that dissipate heat below about 200 ° C., more typically below about 100 ° C. Of these “low temperature” fuel cells, “PEM” fuel cells are the most common. These devices use a polymer membrane, and an electric potential is generated through the polymer membrane. Due to the characteristics of this membrane, the operating temperature of the fuel cell is currently limited to about 100 ° C. In the future, it is expected that this temperature limit will rise to 150 ° C or higher and may approach 200 ° C. A feature of these low temperature fuel cells is that they cannot operate at a sufficiently high temperature so that a typical steam turbine bottoming cycle cannot be used for efficient energy recovery. Various types of PEM cells, such as the “direct methanol” method (where in situ catalytic reforming of methanol and possibly other alcohols or fuels produces hydrogen directly on or near the membrane) It has an operating temperature in the same range.

  The present invention is applicable to integrated fuel reformer / fuel cell power generation systems, as well as non-hybrid or “pure” hydrogen fuel cell power generation systems. An integrated fuel reformer / fuel cell power generation system is a fuel reformer (commonly known as a fuel processor) that converts hydrocarbon-based fuels into reformed fuels that typically contain hydrogen, carbon dioxide, and other trace gases. This reformed fuel is then used in a fuel cell to generate electricity. The fuel processor also typically has an auxiliary device for minimizing the concentration of components harmful to the fuel cell, such as carbon monoxide, which is harmful to the fuel cell.

  In contrast, non-hybrid or “pure” hydrogen fuel cell power generation systems do not use a separate fuel processor or reformer to supply hydrogen fuel to the fuel cell. In non-hybrid systems, hydrogen is typically supplied from a hydrogen storage source such as a pressurized hydrogen gas storage tank, a hydride store in a metal matrix, or liquid hydrogen. In addition, hydrogen storage includes hydrogen that can be easily moved, ie, stored in an unstable chemical form, such as sodium borohydride. In the presence of borohydride, hydrogen can be separated by adding water to the dry chemical. It can also be supplied from a remote source, for example by a hydrogen pipeline. In general, the hydrogen used in non-hybrid fuel cells is a substantially “pure” hydrogen fuel, ie, a fuel that is substantially free of components other than hydrogen, particularly components that are harmful to the fuel cell. .

Embodiment 1
One embodiment of an integrated fuel reformer / fuel cell power generation system of the present invention is schematically illustrated in FIG. A burner 10 is supplied with air / steam 12, fuel 14, and preferably recirculated fuel cell anode exhaust 16, and combusts them to produce hot exhaust 20. Any or all of the burner input (air, fuel, and recirculated fuel cell exhaust) can be preheated by heat exchange in any suitable area, including the heat to be removed. In particular, as will be described below, the air / vapor stream 12 is typically preheated.

  The burner exhaust transfers its heat to the reformer 24 by contact with the wall of the reformer and / or other types of heat exchangers, such as the shell exchanger 26 shown schematically. The reformer is injected with fuel, steam, and optionally oxygen or air, depending on the design of the system (these inputs are not shown for clarity). The heat exchanger 26 can optionally include an additional heat exchanger 28 for superheating the air / steam prior to injection into the burner at 12. The burner exhaust 30 that is not sufficiently cooled then passes through the expander 32 and mechanical energy is recovered from the expander 32. The expander can also be placed at the position indicated by reference numeral 22. This configuration is preferably used in the case of a fuel that can be easily reformed.

  The exhaust then passes through the heat exchanger 34 and subsequently enters the condenser 36 to recover water for recirculation and the residual gas is released. The recirculated water 38 is collected in a tank 40 connected to a pump 42, and water is supplied from the pump 42 to the fuel cell 44. Water that is collected elsewhere in the system is also supplied to the tank.

  The reformed fuel 50 passes through the carbon monoxide removal system 52 except when the fuel cell does not require carbon monoxide removal. The CO removal system is charged with steam, water or air (not shown) and exhausts low CO reformed fuel or hydrogen 54. In the latter case, the dehydrogenated reformed fuel 53 can also be discharged. 53 is recycled to the burner 10 if present. The hydrogen-containing gas 54 then passes through an optional heat exchanger 56. A condenser can be incorporated into the heat exchanger 56 to remove water from the gas, or the heat exchanger 56 can be supplemented with a condenser. The heat exchanger 56 is optional, especially when the CO removal device is a PSA (pressure fluctuation adsorption device) or a membrane separation device. The reformed fuel or hydrogen then enters fuel cell 44 through optional pressure reducing valve 58. The exhaust 60 on the anode side of the fuel cell is recirculated to the burner inlet 16.

  The fuel cell 44 receives pressurized water from the pump 42. The water passes through the heat exchanger 46 in the fuel cell, thereby cooling to remove the heat generated in the fuel cell. This cooling water is sent to the mixer 62. In the mixer, warm cooling water is mixed with the compressed air supplied by the compressor 64, the water evaporates, and the latent air during evaporation is transferred to the resulting air / steam mixture. The amount of compressed air supplied is usually at least 100% above the stoichiometric amount required for hydrogen consumption at full power. If water that does not evaporate is present, it is recycled to water tank 40 through optional radiator 66. Alternatively, some or all of such water is injected into the air / vapor mixture after passing through the fuel cell.

  Compressed and optionally saturated air from mixer 62 enters fuel cell 44 through inlet 68 to supply oxidant to the fuel cell cathode chamber. This air / vapor mixture 70 exits the fuel cell at outlet 72 and is heated by replacement with system components. For example, heating is performed by exchanging with the reformed fuel 50 through the heat exchanger 56 or through a heat exchanger (not shown) located between the CO removal system 52 and the reformer 24. Can do. Cold heat is also recovered by any of a variety of condensers, such as condenser 36, and then enters the hot stage of heating. Further, optionally, the air / steam mixture 70 may be preheated by a heat exchanger in the CO removal section 52. To promote heat absorption, additional water may be added to the air / steam mixture in the cold part of the system, ie from the outlet of the fuel cell to the vicinity of the inlet of the heat exchanger 34. It is possible to add water to the hotter part of the air / steam path, but there are less benefits.

  The air / steam mixture 70 is then heated to a higher temperature by heat exchange with the burner exhaust in the heat exchanger 34. This heat exchange step recovers most of the heat from the burner exhaust after exiting the reformer and expander, thereby preparing the exhaust for condensation for water recovery. The air / steam mixture becomes superheated steam as it exits the exhaust heat exchanger. Water remaining as a liquid in the air / steam mixture is preferably removed before the steam is overheated, for example, recovered in tank 40. As an optional further heating step, the air / steam mixture is further superheated, for example by replacement with exhaust upstream of the expander 28 or by replacement with reformed fuel at 50.

  Finally, an air / steam mixture is fed into the burner from the air / steam inlet 12 and mixed with one or more of the fuel stream, the recycled reformed fuel stream and the anode exhaust stream, Is burned to obtain a hot burner exhaust of about 2000 degrees Fahrenheit (1150 ° C.). In the joint cycle of the present invention, steam is taken into the burner exhaust gas, and the pressure is higher than atmospheric pressure. This creates a further expansion potential compared to a burner exhaust stream that does not contain steam, and this additional expansion potential can be recovered by an expander 32 such as a turbine.

  The expander 32 can be placed at any point on the burner exhaust path, but there is an optimum position depending on the temperature profile of the individual system. In the illustrated system, the preferred location for the expander 32 is after the exhaust heats the reformer 24. With this arrangement, the exhaust can heat the reformer to a temperature of about 1400-1800 degrees Fahrenheit (770-1000 degrees C.) with an initial temperature of 2000 degrees Fahrenheit (1150 degrees C.) or higher. The exhaust is at about 1400-1600 degrees Fahrenheit (770-890 ° C.) and is at a low enough temperature to operate a normal expander such as an automotive expander turbine. It is thermodynamically advantageous to operate the expander at the highest possible temperature.

  The expander is used to generate mechanical power output. The power 82 taken out from the expander by the take-out means can be used, for example, to drive a generator for generating electric power, and the system power output from the fuel cell can be supplemented. This is especially true during system start-up and during system power output, since the start-up and response of the generally slow reforming system can be supplemented by a very rapid increase in the electric drive capacity supplied by the expander. is important. Rapid response is particularly important in transportation equipment applications. The power from the expander can be used to drive mechanical components of the system such as pumps and compressors instead of or in addition to the generator.

  After expansion in a turbine or other expander, the exhaust is cooled to about 200-400 degrees Fahrenheit (110-220 ° C.) by expansion to a pressure approximately equal to atmospheric pressure. The exhaust then heats the incoming steam / air mixture in heat exchanger 34 to separate excess water from the air / water / steam mixture and then passes through condenser 36 to recover the water. This water is returned to the tank, completing the cycle. The exhaust is exhausted from the system at 160.

  The condenser, radiator 36 or other water recovery device, is not necessarily required in all systems, such as stationary power systems or other applications where water recovery is unnecessary or undesirable.

  In applications where water recovery is desired, such as portable applications, it is important to keep the exhaust dew point high enough to enable efficient water recovery. If the ambient temperature is low, for example below 25 ° C., water condensation from the 60 ° C. exhaust stream is easily possible. However, water recovery becomes more difficult when the ambient temperature reaches a high temperature such as 40 ° C. The usual solution to this problem is to size the radiator to the expected worst case ambient temperature, but this can be cumbersome and expensive, especially in portable applications. Since the system of the present invention is pressurized, alternative methods can be used. When the ambient temperature is high, the back pressure can be selectively applied to the exhaust outlet 160 by, for example, the variable flow control valve 170. As air pressure increases and the saturated volume concentration of water in the air decreases, the back pressure increases the dew point of the exhaust stream, thus making it easier to recover the water in the exhaust. For example, if the system is operating at 4 atmospheres, a back pressure of 0.5 atmospheres can increase the dew point by 10-20 ° C. for efficient recovery without increasing radiator dimensions at higher ambient temperatures. to enable. Back pressure comes at the expense of reducing system efficiency because the pressure drop through the expander is reduced. However, the back pressure can be adjusted to the minimum required to recover enough water under ambient conditions, so that, for example, the system in a vehicle can be adjusted to those under various temperature and weather conditions. It is possible to operate while maintaining the maximum efficiency possible under the conditions.

Embodiment 2
A second exemplary embodiment of the integrated fuel reformer / fuel cell power generation system of the present invention is shown in FIG. This embodiment is similar to the embodiment shown in FIG. 1 except that the pressurized air / steam mixture is now generated (at least in part) by direct injection of water into the fuel cell stack. Thus, the injected water accomplishes two functions: humidification of the cathode air and cooling of the fuel cell. The direct injection of water for humidification / cooling of fuel cells is described in the international patent application no. PCT / EP00 / 03171 (International Publication No. WO00 / 63992), which is hereby incorporated by reference herein in its entirety. Direct water injection can be used as a supplement or replacement for the previously described fuel cell cooling loop. As shown in FIG. 2, the saturator / mixer 62 (FIG. 1) has been replaced with an injector 80 and a pump 81. Water is supplied to the injector 80 in a desired amount by the pump 81 and injected into the fuel cell stack. The water may be injected into the separated mixing device, mixed with the cathode air, and then injected integrally into the fuel cell. The amount of water sprayed is determined by the system controller so that the temperature of the stack is adjusted to a predetermined level, and water can be supplied without shortage to remove enough heat from the stack by vaporization of the water. This vaporization also causes the cathode air to be nearly or completely saturated, producing a vapor-containing exhaust stream 70 from the stack. If necessary, additional water may be added to the air / steam stream 70 at other locations in the system. For example, heat from the reformed fuel 54 and the burner exhaust 30 can be utilized in the heat exchanger 56 or 34, respectively, to evaporate additional water into the fluid 70. In addition, the cooling loop can be used simultaneously with the direct injection of water, and heat can be controlled under a wide variety of conditions such as when the burner 10 is not used.

According to the calculation of the increase in efficiency system efficiency in the above embodiment, the entire fuel cell heat recovery system shown here can be significantly improved. The exact value depends on the operating state of the system and a number of additional variables (variables). Typical values for system efficiency in portable systems are in the range of about 30-35%. By recovering half of the energy value of the fuel cell waste heat, for example from 35% system efficiency to 41% (15% increase in efficiency), the system efficiency is at least 5%, more typically 15%. This can be improved. The waste heat of the fuel cell can be recovered at a higher rate, and the efficiency can be further increased. For higher efficiency, an additional supply of air may be required, but as mentioned above, that air does not necessarily have to pass through the fuel cell.

  In addition to improving the efficiency by recovering heat from the fuel cell by vaporizing water and driving the expander using the steam, attention is paid to improving the efficiency by using the expanded exhaust to preheat the feed to the burner. Should. This is made possible by recovering 100% of the additional fuel energy required to drive the expander. Normally, a separate recuperator cannot fully recover the energy input used to drive the expander.

  To understand how this is possible, consider the heat exchanger 34 of FIG. 1 that functions as an expander recuperator in the configuration disclosed herein. The input air / steam 70 has a specific temperature, for example, 200 ° F. (about 95 ° C.), and the design temperature of the output to the condenser 36 is, for example, 400 ° F. (about 205 ° C.). If there is no expander in the system, the burner exhaust enters heat exchanger 34 at about 1600 degrees Fahrenheit (about 890 ° C) and the air / steam mixture is recuperator at about 1400 degrees Fahrenheit (about 780 ° C). Will leave. The inefficiency of this step is inherent in this design. On the other hand, if an expander 32 is present in the system, the burner exhaust enters the recuperator at a temperature of about 1300 degrees Fahrenheit (about 720 ° C.). Thus, the air / steam flow will exit the recuperator at only about 1100 degrees Fahrenheit (about 610 ° C.). This difference of 300 degrees Fahrenheit (about 165 ° C) is compensated by burning additional fuel in the burner, and the burner exhaust leaves the burner 10 at about 1800 to 2000 degrees Fahrenheit (about 1000 to 1100 ° C) The reformer 24 is heated. However, this energy is the energy itself that is recovered by the expander when the exhaust is reduced from 1600 degrees Fahrenheit to 1300 degrees Fahrenheit (from about 890 ° C. to about 720 ° C.) as it passes through the expander. Thus, since all of the heat applied to drive the expander is recovered, the expander is more efficient and 100% efficient than a system without an expander.

  It is thus particularly advantageous in this embodiment of the joint cycle to provide a heat exchanger operating between the air / steam flow supply and the burner exhaust as the main recuperator of the expander.

  Efficiency improvements in this range are important in three ways. First, the efficiency of a system including a joint cycle can approach the efficiency of a bottoming cycle internal combustion engine while maintaining the fuel cell advantage of low emissions. Secondly, the joint cycle saves heat and waste into the environment, allowing the use of smaller fuel cells and fuel generators for a given power output, saving weight and cost. Third, the higher efficiency directly leads to the miniaturization of heat waste means such as a radiator that is a condenser for a given power level. Because the second and third effects are multiplied, the reduction in radiator area is potentially very large.

  The key principle of this joint cycle is to extract energy from these waste heats by evaporating the water into the compressed air using the low temperature “waste” heat, especially the waste heat from fuel cell operation. . The resulting air / steam or air / steam / water mixture is then heated in a suitable manner and finally injected into the expander at elevated temperature and pressure. The expander is used to generate mechanical work. The net mechanical work generated is given to the air / steam / water mixture by vaporization of water and corresponds to the latent heat taken away from the cooling water and the like. The absorbed latent heat is the basis for the net energy gain achieved through the use of a joint cycle.

  The joint cycle, which is a combination of vaporization, heating and expansion as described above, is in principle suitable for improving the efficiency of any fuel cell based power system. Although more complex, it is most applicable when it is difficult to use for direct steam generation because the waste heat to be recovered is cold. This is particularly advantageous in PEM fuel cells where the upper operating temperature is usually below about 100 ° C. However, it should be noted that in joint cycle applications to higher temperature PEM membranes, using a larger amount of steam and operating at higher pressures will result in greater output.

  Depending on the exact type of each module that makes up the system, adjustments may be required, particularly in the details of heat transfer and exchange, and several options are being considered. In the embodiment of FIG. 1, the reformer is shown as a steam reformer, but at least some partial oxidation can be used, either in a separate module or in autothermal mode. The carbon monoxide removal system may be a combination of water gas shift and selective oxidation, or may be PSA, TSA, selective methanogenesis, or hydrogen selective membrane with or without water gas shift. In principle, any expander is useful, but a turbine is the preferred option in terms of a small, lightweight commercial expander that operates in the range of 1000-2000 degrees Fahrenheit (550-1150 ° C.).

  In the development of fuel cell technology, improving system efficiency has been a goal over the years. Therefore, the improvement of the fuel reformer / fuel cell system brought about by the incorporation of the joint cycle of the present invention is important and is expected to boost the commercial success of the integrated fuel reformer / fuel cell system.

Embodiment 3
The “joint cycle” is also applicable to a system not equipped with a reformer. By adding a burner to burn excess fuel from the anode and using the waste heat of the fuel cell to vaporize water into the compressed air, a steam-containing exhaust stream can be supplied to the expander, Waste heat can be recovered as mechanical energy.

  An example of a non-hybrid “pure” hydrogen fuel cell power generation system of the present invention is schematically illustrated in FIG. A fuel cell stack 110 such as a PEM stack has an anode chamber 112, a cathode chamber 114, and a cooling device 116. Hydrogen is supplied to the anode 112 from a pressurized supply source 120 such as a storage tank. The cathode 114 is supplied with an oxygen-containing gas, preferably consisting of a pressurized air / steam mixture. An electrochemical reaction between the hydrogen and the oxygen-containing reactant in the fuel cell generates electrical power.

  In addition to the useful power, the fuel cell also generates waste heat, which is removed from the fuel cell stack by the cooling device 116. The cooling device 116 generally has a cooling loop portion 130 that is in thermal contact with the cathode portion 114 and the anode portion 112 of the fuel cell 110. Pressurized cooling water is driven by the pump 132 and circulates through the cooling device 116. Waste heat from the fuel cell 110 is transmitted to the low-temperature cooling water, and the cooling water is sent out of the fuel cell 110 to remove the waste heat from the cells. After exiting the fuel cell 110, the heated cooling water is supplied to the saturator 134. The saturator 134 is supplied with air that has entered through the air inlet 122 and has been pressurized by the compressor 124 via a path 136. Part of the hot water (about 60-70 ° C.) from the cooling loop 130 is vaporized into the compressed air 136 to produce a saturated mixture of air and steam. The evaporation of warm water into a pressurized gas, usually air or other oxidant, is commonly referred to as “partial pressure boiling”.

  The water is heated directly as cooling water or indirectly by heat exchange with cooling water or exhaust. The water is pressurized and mixed with pressurized air and saturates some or all of the air with water at a temperature approximately equal to or below that of the cooling water. The partial pressure boiling of the cooling water into the pressurized air may be achieved by an external saturator 134 as shown in FIG. 3, or may be accomplished within the fuel cell stack 110 (as described in more detail below). It will be understood that this may be done. In addition, optionally, some or all of the partial pressure boiling can occur downstream of the fuel cell stack 110 rather than before the pressurized air stream enters the cathode as shown in FIG.

  Returning to the embodiment of FIG. 3, air saturated with water is carried to fuel cell cathode 114 via path 138 and functions as an oxidizing reactant for the fuel cell. The air-vapor mixture then exits the fuel cell as exhaust, and the cathode exhaust 146 containing the moisture is conveyed to the burner 140.

  In this embodiment, the anode side 112 of the stack typically operates in a “dead end” mode. That is, the anode outlet is closed by a purge valve 119, which purge valve 119 opens at certain time intervals to discharge the anode exhaust 118 containing some unused hydrogen and condensate from the stack. Like the cathode exhaust 146, the purged anode exhaust 118 is also supplied to the burner 140.

  In the burner 140, all the hydrogen contained in the anode exhaust 118 is combusted with the steam / air mixture of the cathode exhaust 146, creating a hot steam-containing exhaust stream 142. Further, preferably, the burner 140 is supplied with additional hydrogen fuel from the hydrogen source 120 and enters the burner 140 through a controllable throttle valve 126. Optionally, fuel from other sources, including non-hydrogen fuels, can be used to supply the excess fuel needed beyond that provided by the anode exhaust.

  In general, the amount of fuel required to operate the burner (including anode exhaust fuel and other fuels) is up to approximately half of the amount of fuel required for the fuel cell. To supply fuel to the burner, the fuel cell can be configured to bypass the large amount of hydrogen and supply the burner (ie, the fuel cell does not necessarily have to be operated in a “dead end” mode). This can reduce the membrane electrode area required for a given power output, which in turn can reduce the cost of the power system. This is because electrode area accounts for a significant portion of the cost of the system because of platinum or other expensive material in the catalyst.

  The pressurized steam-containing exhaust stream 142 exiting the burner 140 is then expanded through an expander 144, usually a turbine, to generate mechanical output. The mechanical output from the expander 144 can be used to drive a compressor 124 that provides a pressurized air stream 136. Further, the mechanical output from the expander 144 can be used to drive a generator to generate electrical power via extraction power 82 and / or mechanical of a system such as a pump or compressor. It can be used to drive the components and / or otherwise supplement the output of the system. The position of the expander is preferably a position downstream of the burner and following the burner. However, if the expander cannot withstand the high temperature in such an arrangement, the burner exhaust is first supplied with, for example, fuel or heat flowing from the valve 126. The exhaust can enter the expander 144 after some cooling by heat exchange with a suitable fluid, such as the air-vapor stream 146 from the exchanger 148.

  The pressurized air-vapor exhaust stream 146 from the cathode is preferably preheated prior to introduction into the burner 140. For example, as shown in FIG. 3, the air / steam cathode exhaust stream 146 is heated in a heat exchanger / recuperator 148 by heat exchange with the expanded turbine exhaust 150. Optionally, instead of or in addition to preheating the introduction to the burner by heat exchange with the exhaust after expansion, the preheating before introduction to the burner is exchanged with the exhaust before expansion (not shown). May be performed. Heat exchange with the exhaust stream prior to expansion will produce some less energy in the expander, but lower exhaust temperatures allow the use of less expensive expanders.

  Finally, the cooled exhaust stream 152 passes through a preheating heat exchanger 148 and then preferably passes through a condenser radiator 154 for recovering water. Water from the condenser radiator 154 is collected in the tank 156 and supplied to the saturator 134 by the pump 158. Cooled exhaust stream 160 exits the system at exhaust outlet 160. As in the embodiment of FIGS. 1 and 2, the back pressure can be selectively applied to the exhaust outlet 160 by, for example, a variable flow control valve 170. The back pressure increases the dew point of the exhaust stream (because the saturated volume concentration of water in the air decreases with increasing air pressure), which makes it easier to recover the water in the exhaust in high ambient temperatures become.

  It will be appreciated that there are systems that do not require a condensing radiator 154 or other water recovery device, such as stationary power systems or other applications where water recovery is not required or desirable.

  The present invention has significant advantages over conventional non-hybrid hydrogen fuel cell systems. By recovering some of the low quality waste heat from the stack as mechanical or electrical power, the net power at a given fuel cell size is increased. In addition, burning the excess hydrogen and / or other fuel in the burner increases the dew point of the exhaust, making full water recirculation easier at reasonable radiator sizes and reducing waste heat. Since some is recovered, less heat is wasted. In addition, the pressure of the air flow to the cathode increases the efficiency of the fuel cell, and the extra power required to compress this air is offset by the heat recovery by the expander turbine. The cycle efficiency of the turbine is increased due to the addition of a free latent heat Rankine cycle.

Embodiment 4
Turning now to FIG. 4, another embodiment of the pure hydrogen fuel cell power generation system of the present invention is shown, in which water is injected directly into the fuel cell for both humidification and cooling. The water is vaporized in the pressurized air. Similar to the embodiment of FIG. 2, in this example, the cooling loop and saturator 132 of FIG. 3 has been replaced by an injector / mixer 180 that is pumped from a tank 156 by a pump 158 ′. Water is being supplied. This injector mixes the water with the pressurized air from the compressor 124 and injects the water / air mixture onto the cathode 114 of the fuel cell 110. This water cools and humidifies the fuel cell, and at least a portion of this water vaporizes into the cathode air, producing a pressurized air / steam mixture 146 that is used in the burner 140. Injection / mixing can be performed by a separate apparatus 180 as shown here, or it is possible to inject water directly into the stack for mixing with pressurized cathode air. If necessary, heat from the burner exhaust can be used to vaporize additional water into the cathode exhaust 146 before or in the recuperator 148. In order to enable heat control under a wide variety of situations, for example when a burner is not used, an intermediate configuration with a cooling loop is also possible.

Other components and features of the system Where any heat exchange is desired or required in any of the embodiments of the invention described above, any heat exchange or heat known or utilized by those skilled in the art. The method of transmission is also suitable for the present invention. If feasible, integrating modules in one or more common housings is an effective way to provide efficient heat transfer. Thus, the reforming zone may be arranged in a ring around the burner zone or within the burner zone. Furthermore, heat transfer between the zones may be performed by a normal heat exchanger such as a tube or other hollow structure, or may be transmitted by a passive element such as a fin.

  Also, in principle, any type of expander can be used to improve system efficiency, but in the above embodiment, it is currently preferred to use a turbine as the expander. The advantages of turbines are high temperatures such as 1200-1600 degrees Fahrenheit (about 650-900 ° C.) that are equal to or lower than the preferred temperature for catalyzing the reforming reaction when using fuels such as gasoline, propane or methane. However, it is possible to use a turbine that can operate with high reliability. For other fuels such as methanol, the temperature of the reforming reaction will be lower. It is highly desirable to operate the expander at the highest possible temperature in order to obtain maximum net mechanical work, ie work that exceeds the work consumed to compress the air at the beginning of the waste heat recovery process. . Turbines can be disadvantageous in that their efficiency exhibits a sharp peak at a particular gas flow rate. In the system of the present invention, this is compensated by sizing the compressed air / water heat exchange to remove approximately 40% to 50% of the excess fuel cell heat generated at maximum load. Can do. As a result, the flow rate of compressed air entering the system can be maintained at a constant level from about 40% to 100% of the maximum output, and the efficiency of waste heat recovery can be maintained. The remaining part of the waste heat can be removed by conventional heat exchange methods.

  Another method is to inject further water, particularly water used to cool the fuel cell or water that has been heated in the performance of heat exchange, into the air / steam path behind the fuel cell and before injection into the burner. This allows further recovery of low temperature energy while maintaining the volumetric flow rate in the appropriate range for the expander. In addition, if the optimal air flow causes drying in a fuel cell such as a PEM fuel cell, some of the compressed air or air / steam has passed through the fuel cell for heating, bypassing the fuel cell. Can be combined with cathode exhaust.

  Due to the high temperatures required, the placement of expanders in the system is limited. In order to obtain maximum efficiency, the temperature of the expander should be as high as possible. In a typical metal turbine, this is in the range of about 1000-1600 degrees Fahrenheit (about 450-900 ° C), with about 1300-1500 degrees Fahrenheit (about 720-850 ° C) being particularly preferred. This means that the turbine cannot be directly exposed to exhaust, which is typically about 1800 to 2000 degrees Fahrenheit (about 1000 to 1150 ° C.). Thus, if a reformer is present (as in Embodiments 1 and 2 above), it is preferred that the exhaust be first used to heat the reformer and then expand in the turbine. This is also preferred to maximize the temperature of the reforming reaction. However, when using fuels that are unstable and easy to reform at low temperatures, such as methanol, a higher temperature in the range of about 1600 to 2000 degrees Fahrenheit (about 850 to 1150 ° C.), such as a ceramic turbine. It may be preferable to use an inflator that can be operated on and be placed as the first component downstream of the burner. As a result, cooler gas can be used to heat the reformer. Although not readily available, other high temperature resistant expanders, particularly positive pressure expanders, can be used in the present invention to recover the energy of the heated air / steam mixture in the burner exhaust.

  Another method of supplying hydrogen without a reformer is direct oxidation of fuel at the anode. Methanol is particularly suitable for such applications, but other alcohols can be used (see, eg, US Pat. No. 6,423,203 for a description of such use). These “reformerless” fuel cells are advantageous in terms of efficiency when used in the aforementioned systems of “pure” hydrogen fuel type fuel cells. As much of the waste heat is consumed for fuel reforming at the anode, less waste heat will be available. However, the use of this waste heat for fuel reforming is often less efficient than a fuel cell fed with hydrogen or reformed fuel, so that anode exhaust is less than the fuel feed required for the burner. Many parts will be supplied. In addition, the anode exhaust can provide some vaporized water as long as the fuel contains some water or, if previously vaporized, contains water vapor. In such a case, a “direct mode” fuel cell can be considered as a source of hydrogen itself, and thus such an embodiment provides sufficient efficiency improvement to recover the incidental costs of burners and expanders. If provided, it is included within the scope of the present invention.

  Although the present invention has been shown and described in detail with reference to the preferred embodiments, it is understood that various changes in form and details are possible within the scope of the invention included in the appended claims. Those skilled in the art will understand.

FIG. 1 is a schematic system diagram of an integrated fuel cell / fuel reformer power generation system of the present invention. FIG. 2 is a schematic system diagram of an integrated fuel cell / fuel reformer power generation system using direct water injection. FIG. 3 is a schematic system diagram of a non-hybrid hydrogen fuel cell power generation system according to another embodiment of the present invention. FIG. 4 is a schematic system diagram of a hydrogen fuel cell power generation system using direct injection of water.

Explanation of symbols

10 Burner 12 Pressurized Air / Steam Mixture 14 Fuel 32 Expander 36 Condenser 40 Tank 42 Pump 44 Fuel Cell 64 Compressor 82 Output Extraction 110 Fuel Cell 112 Anode 114 Cathode 124 Compressor 140 Burner 144 Expander (Turbine)
154 Condenser (Radiator)
156 (Water) tank 158 Pump 170 Flow control valve

Claims (47)

A fuel cell having an anode and a cathode;
And a hydrogen fuel source to supply hydrogen fuel to the anode of the fuel cell,
A compressor for generating a pressurized air flow, wherein the generated compressed air flow is supplied to a cathode of the fuel cell, and reacts with hydrogen of the anode in the fuel cell membrane to generate electric power and waste heat. A compressor,
A liquid supply source that communicates with the pressurized air flow to supply a liquid that is directly injected as a liquid into the fuel cell, wherein at least a portion of the liquid from the supply source is heated by waste heat of the power generation system A liquid source that vaporizes into the pressurized air stream to produce a pressurized mixture of air and steam;
Burning a burner fuel with the pressurized air / steam mixture to produce a steam-containing exhaust stream;
An expander in communication with the burner, the expander being driven by the steam-containing exhaust stream and generating an output exceeding the power required for pressurizing the air;
The hydrogen fuel is selected from the group consisting of hydrogen gas and at least one alcohol;
The hydrogen gas is supplied from a source different from a fuel reforming unit provided individually in each system,
The at least one alcohol is at least partially reformed at the anode of the fuel cell so as to generate hydrogen directly at or near the fuel cell membrane;
A fuel cell power generation system for taking out the excess output as power from the expander.   2. The system of claim 1, wherein the extracted power is used to drive a generator.   The system of claim 1, wherein the extracted power is used to drive at least one component in the power generation system.   4. The system of claim 3, wherein at least one component of the system includes at least one of a compressor and a pump.   The system of claim 1, wherein the expander includes a turbine. According to claim 1, wherein the hydrogen fuel is methanol, the fuel cell membrane or to produce hydrogen directly in the fuel cell juxtamembrane, at least in part in the anode of the fuel cell is one that was modified system. 2. The system according to claim 1 , wherein the hydrogen fuel is hydrogen gas . 8. The system according to claim 7 , wherein the burner fuel includes unreacted hydrogen discharged from the anode. 8. The system of claim 7 , wherein the burner fuel includes additional fuel from a source other than the anode of the fuel cell. According to claim 9, wherein the additional fuel comprises hydrogen gas, a source other than the anode of the fuel cell consists of a source of the hydrogen fuel system. 11. The system according to claim 10 , further comprising a throttle valve for selectively supplying the additional fuel to the burner. 9. The system according to claim 8 , further comprising a purge valve for selectively supplying exhaust from the anode of the fuel cell to the burner. 8. The system of claim 7 , further comprising a heat exchanger for transferring heat from the burner exhaust to at least one fluid. 14. The system of claim 13 , wherein the fluid includes an input to a burner. 14. The system of claim 13 , wherein the heat exchanger transfers heat from the burner exhaust after the burner exhaust passes through the expander. 14. The system of claim 13 , wherein the heat exchanger transfers heat from the burner exhaust before the burner exhaust passes through the expander.   2. The system of claim 1, further comprising a condenser that recovers steam from the burner exhaust before discharging the burner exhaust from the system. 18. The system of claim 17 , further comprising a device that selectively applies a back pressure to the burner exhaust to facilitate recovery of steam in the burner exhaust.   The system of claim 1, further comprising a cooling fluid that circulates through the system to remove waste heat from the fuel cell. 20. The system according to claim 19 , wherein the source of liquid that vaporizes into the pressurized air includes a cooling fluid. 20. The system of claim 19 , wherein the source of liquid that vaporizes into the pressurized air is heated by waste heat from the cooling fluid.   2. The system of claim 1, wherein the liquid is vaporized into the pressurized air stream within the fuel cell. The system according to claim 1, wherein the fuel cell has an operating temperature of 200 ° C or lower .   The system of claim 1, wherein the fuel cell is a PEM fuel cell. A method for efficient operation of a fuel cell power generation system, comprising:
A step of supplying hydrogen fuel to the anode of the fuel cell from the hydrogen fuel supply source,
A process of compressing an oxygen-containing gas to generate a pressurized air stream;
Supplying the pressurized air to the cathode of the fuel cell;
Reacting the hydrogen and the pressurized air in the fuel cell to generate electric power and waste heat;
Injecting liquid directly into the fuel cell and evaporating the liquid into pressurized air in the fuel cell to produce a pressurized air / vapor mixture;
Combusting burner fuel with the pressurized air / steam mixture to produce a hot steam-containing exhaust stream;
Expanding the hot steam-containing exhaust stream with an expander to produce an output that exceeds the power required to supply the pressurized air stream;
Look including a step of taking out the excess output from said expander,
In the hydrogen fuel supply process,
The hydrogen fuel is selected from the group consisting of hydrogen gas and at least one alcohol;
The hydrogen gas is supplied from a source different from the fuel reforming unit provided individually in each system,
Reforming at least a portion of the at least one alcohol at the anode of the fuel cell to produce hydrogen directly at or near the fuel cell membrane;
Method. 26. The method of claim 25 , wherein extracting excess output includes using the output to drive a generator. 26. The method of claim 25 , wherein the step of extracting excess output includes driving a component of the power generation system. 28. The method of claim 27 , wherein the component includes at least one of a pump and a compressor. 26. The method of claim 25 , wherein the expander includes a turbine. 26. The method of claim 25 , wherein the step of vaporizing liquid in pressurized air is performed before the air stream enters the fuel cell. 26. The method according to claim 25 , wherein the step of vaporizing the liquid in the pressurized air is performed in the fuel cell. 26. The process of claim 25 , further comprising circulating a cooling fluid in the system to remove waste heat from the fuel cell, and liquid in pressurized air using the waste heat from the circulating cooling fluid. A method including the process of vaporizing. 33. The method of claim 32 , wherein the fluid that vaporizes into the pressurized air comprises a circulating cooling fluid. According to claim 25, wherein said fuel cell has an operating temperature of 200 ° C. or less. 26. The method of claim 25 , wherein the fuel cell is a PEM fuel cell. According to claim 25, wherein the hydrogen fuel is methanol, the fuel cell membrane or to produce hydrogen directly in the fuel cell juxtamembrane, at least in part in the anode of the fuel cell is one that was modified Method. 26. The method of claim 25 , wherein the hydrogen fuel is hydrogen gas . In claim 25 , further
Releasing the exhaust containing unreacted hydrogen from the anode of the fuel cell, and combusting the unreacted hydrogen together with the pressurized air / steam mixture to produce the hot steam-containing exhaust stream. A method that includes a process. 26. The method of claim 25 , wherein the burner fuel comprises additional fuel from a source other than the anode of the fuel cell. According to claim 39, wherein the additional fuel is contains a hydrogen gas, a method of a source other than the anode of the fuel cell, consisting of the hydrogen fuel supply. 26. The method of claim 25 , further comprising preheating at least one of the burner fuel and the pressurized air / steam mixture prior to combustion. 42. The method of claim 41 , wherein the preheating step includes supplying heat from the hot steam-containing exhaust stream. 26. The method of claim 25 , further comprising recovering condensed vapor from the exhaust stream prior to releasing the exhaust from the system. 44. The method of claim 43 , further comprising selectively applying a back pressure to the exhaust stream to facilitate recovery of vapor condensed from the exhaust. A fuel cell having an anode and a cathode;
A supply source for supplying hydrogen gas to the anode of the fuel cell, wherein the supply source of hydrogen gas is different from the fuel reforming unit disposed individually in each system;
A compressor that generates a flow of pressurized air, supplying the generated pressurized air flow to the cathode of the fuel cell and reacting with the hydrogen gas of the anode in the fuel cell membrane to generate power and waste heat. A compressor to let
A liquid supply source that communicates with the pressurized air flow to supply a liquid that is directly injected as a liquid into the fuel cell, wherein at least a portion of the liquid from the supply source is heated by waste heat of the power generation system A liquid source that is vaporized into the pressurized air stream to produce a pressurized mixture of air and steam;
A burner for burning fuel together with the pressurized air / steam mixture to produce a steam-containing exhaust stream;
A non-hybrid hydrogen fuel cell power generation system having an expander that communicates with the burner and is driven by the steam-containing exhaust stream to generate output. According to claim 45, wherein the source of hydrogen gas, a source of stored hydrogen system. A method for efficient operation of a non-hybrid hydrogen fuel cell power generation system, comprising:
Supplying hydrogen to the anode of the fuel cell from a source different from the fuel reforming unit individually disposed in each system;
A process of compressing an oxygen-containing gas to generate a pressurized air stream;
Supplying the pressurized air to the cathode of the fuel cell;
Reacting the hydrogen and the pressurized air in the fuel cell to generate electric power and waste heat;
Injecting liquid directly into the fuel cell and evaporating the liquid into pressurized air in the fuel cell to produce a pressurized air / vapor mixture;
Combusting fuel with the pressurized air / steam mixture to produce a hot steam-containing exhaust stream;
Expanding the hot steam-containing exhaust stream with an expander to produce an output.

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